Thermally conductive materials include elastomeric materials such as CHO-THERM.RTM. thermal pads, films, such as KAPTON.RTM. MT thermally conductive polyimide film, tapes, such THERMATTACH.RTM. pressure sensitive acrylic tapes, and adhesives and greases, such as silicone grease, all of which contain a thermally conductive filler in a resin binder. They are primarily used in electronic applications where good thermal conduction is needed. For example, a thermally conductive material may be used as an interface between a heat source, such as semiconductor or other electronic component and a metal heat sink.
Many electronic designs and applications are limited by the ability to dissipate thermal energy generated during the operation of the electronic components. Many electronic components, especially semiconductor components, are prone to breakdown at high temperatures. Thus, the ability to dissipate heat is a limiting factor on the performance of the component.
Thermally conductive materials have been based upon the use of a binder, preferably a resin binder in particular a silicone, thermoplastic rubber, urethane or acrylic, into which one or more thermally conductive fillers have been distributed.
These fillers have typically been one of two major types: thermally conductive, electrically insulative or thermally conductive, electrically conductive fillers.
Aluminum oxide, magnesium oxide, zinc oxide, boron nitride and aluminum nitride are the most often cited types of thermally conductive, electrically insulative fillers used in thermal products. Aluminum, copper, graphite, nickel and silver are commonly cited examples of thermally conductive, electrically conductive fillers.
In using such materials, it is known that by applying pressure between the heat source and the heat sink, one is able to obtain higher apparent thermal conductivity from the thermal product which is located between the heat source and heat sink. Typically, pressures of up to 300 psi are used in order to obtain the maximum apparent thermal conductivity possible from the product.
What is desired is a thermally conductive filler with higher thermal properties. Moreover, it is desired to have a thermally conductive material which has satisfactory thermal properties at low or no applied pressures.
The present invention provides such a material.